JP3976373B2 - Pneumatic tire manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a manufacturing how the pneumatic tire having a belt ply corrugated code is embedded.
[0002]
[Prior art]
Conventionally, a pneumatic tire is formed into a cylindrical shape while forming a cylindrical green case by, for example, winding a carcass ply around the outer periphery of a cylindrical forming drum and then setting a bead and turning it back. After a plurality of belt plies are wound around the outer periphery of the band forming drum, a tread is wound around the outer side of the belt ply in the radial direction to form a BT (belt tread) band. A green tire is formed by fitting and attaching the BT band to the outside in the radial direction of the green case while bulging into a shape, and then forming the green tire by vulcanizing with a vulcanizer. Yes. Such molding is similarly performed when the belt ply includes a parallel belt ply that is arranged so as to be substantially parallel to the circumferential direction and in which a cord bent in a wave shape is embedded.
[0003]
[Problems to be solved by the invention]
Even in the pneumatic tire including the parallel belt ply as described above, the belt layer including the parallel belt ply is wound around the outer periphery of the cylindrical band forming drum to form the cylindrical belt layer. However, such a belt layer is deformed so that the central portion in the width direction protrudes radially outward from both ends in the width direction during vulcanization of the green tire, and is usually deformed to curve with a certain radius of curvature. On the way, the corrugated cords embedded in the central portion in the width direction of the parallel belt ply are stretched in the circumferential direction larger than the corrugated cords embedded in both ends in the width direction. As a result, in the vulcanized pneumatic tire, the wavelength of the wavy cord in the parallel belt ply gradually decreases and the amplitude gradually increases from the center in the width direction toward both ends in the width direction. There is a problem that the rigidity in the circumferential direction, i.e., the tightening effect is weakened and the belt end separation cannot be effectively suppressed.
[0004]
It is an object of the present invention to provide a pneumatic tire in which belt durability is improved by enhancing circumferential rigidity at the belt end, that is, an effect of tightening.
[0005]
[Means for Solving the Problems]
These objects, inclined belt ply cord is inclined with respect to the tire equatorial plane are buried in the interior, and, together with the parallel belt ply cord bent in a wave shape is embedded therein is wound around the outer periphery, It has a drum shape with its radius decreasing from the center in the axial direction toward both outer sides in the axial direction, and is separated from the center in the axial direction and the center in the axial direction to both outer sides in the axial direction by a half width of the parallel belt ply. A step of preparing a tire molding drum in which a difference in radius between the center and the width of the vulcanized pneumatic tire having the parallel belt ply is equal to or greater than a difference in radius between the center in the width direction and both ends in the width direction; By winding a plurality of inclined belt plies and parallel belt plies around the drum-shaped drum, the cords in the parallel belt plies are arranged in the circumferential direction. A belt layer is formed while being arranged so as to be substantially parallel, and thereafter, a tread is wound around the outer side of the belt layer in the radial direction to form a pneumatic tire band, and a radial direction of the green case is expanded it can be achieved by Rukoto comprising the steps of: forming a joining green tire fitted to the band of the pneumatic tire to the outside, and a step of manufacturing a pneumatic tire by vulcanizing the green tire.
[0006]
When the green tire is vulcanized as described above, the center portion in the width direction of the parallel belt ply is greatly stretched in the circumferential direction. Therefore, when the vulcanized pneumatic tire is obtained, the center portion in the width direction of the parallel belt ply is obtained. The value B obtained by dividing the amplitude a of the wavy cord embedded in the wavelength by the wavelength λ is considerably smaller than the value at the time of the green tire, and the circumferential rigidity, that is, the tightening effect is increased. For this reason, in the present invention, the value A of a / λ at both ends in the width direction of the parallel belt ply in the vulcanized pneumatic tire is equal to or less than the value B of a / λ at the center in the width direction described above. The same or less than the value B, thereby enhancing the circumferential rigidity at both ends in the width direction of the parallel belt ply, that is, the effect of tightening more than the circumferential rigidity at the center in the width direction, thereby effectively separating the belt end separation. I tried to suppress it.
[0007]
Here, in order to form the green tire described above, a belt layer is formed by winding a plurality of belt plies including parallel belt plies around the outer periphery of the drum, and then a tread is wound around the outer side in the radial direction of the belt layer. Thus, it is necessary to form a band composed of the belt layer and the tread. By making the radius of the drum for forming such a band smaller from the center in the axial direction toward the both outer sides in the axial direction, the drum is formed into a drum shape. And the difference in radius between the axial center of the drum and the position separated from the axial center by one-half the width of the parallel belt ply to the outside in the axial direction is vulcanized air having the parallel belt ply. If the radial difference between the center in the width direction of the parallel belt ply and the both ends in the width direction of the tire is greater than or equal to the width of the parallel belt ply, The central portion in the width direction is the same at both ends in the width direction or larger at both width ends than the central portion in the width direction, and as a result, the circumference of the corrugated cord embedded in the width direction both ends of the parallel belt ply is vulcanized. The amount of stretching in the direction is equal to or greater than the amount of stretching of the wavy cord embedded in the center in the width direction. Thus, when it becomes vulcanized pneumatic tire, it is less than or equal to the value B of a / lambda in the value A is the widthwise central portion of a / lambda in the width direction both end portions of the parallel belt ply, the pneumatic tire of the above It can be molded easily and reliably.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In FIGS. 1, 2, and 3, 11 is a pneumatic radial tire as a product for which vulcanization has already been completed. This tire 11 includes a pair of bead portions 13 each embedded with a bead core 12, and these bead portions 13 Side wall portions 14 extending outward in the radial direction from each other, and a substantially cylindrical tread portion 15 connecting the outer ends in the radial direction of the side wall portions 14. The tire 11 is reinforced by a toroidal carcass layer 21 extending from one bead portion 13 to the other bead portion 13, and both end portions in the width direction of the carcass layer 21 are around the bead core 12. It is folded back from the axially inner side toward the axially outer side. The carcass layer 21 is composed of at least one carcass ply 22 in this embodiment. The carcass ply 22 is made of a large number of steels perpendicular to the tire equatorial plane E (extending in the radial direction). A non-extensible cord 23 is embedded. A belt layer 25 is disposed on the radially outer side of the carcass layer 21, and a plurality of belt layers 25, in this embodiment, five belt plies 26, that is, first, second, third, fourth, and fifth belt plies 26a. , 26b, 26c, 26d, and 26e are sequentially overlapped from the radially inner side to the radially outer side. Here, at least one belt ply of the belt plies 26, in this embodiment, the three belt plies of the first, second, and fifth belt plies 26a, 26b, and 26e are arranged in the circumferential direction, that is, tires. Inclined belt plies in which a large number of cords 27 that are inclined at an angle of 10 to 50 degrees with respect to the equatorial plane E are embedded, and these cords 27 are made of steel, kevlar (aromatic polyamide fiber), etc. Constructed from extensible material. These cords 27 intersect at least two inclined belt plies when there are a plurality of inclined belt plies. On the other hand, at least one belt ply of the belt plies 26, and in this embodiment, the two belt plies of the third and fourth belt plies 26c and 26d are arranged so as to be substantially parallel to the circumferential direction. These are parallel belt plies in which cords 28 arranged so as to be substantially parallel to the tire equatorial plane 5 are embedded, and these cords 28 are made of a non-extensible material such as steel. Here, these cords 28 are bent in a wave shape in a plane parallel to the front and back surfaces of the third and fourth belt plies 26c, 26d, for example, a square wave shape, a triangular wave shape, and a sine wave shape, and the amplitude is a, The wavelength is λ. Note that the cords 23, 27, and 28 described above may be formed by twisting a plurality of filaments, or may be formed of a single filament. Further, on the outer side in the radial direction of the belt layer 25, a tread 31 having a groove 30 such as a main groove or a lateral groove formed on the outer periphery is disposed. The outer periphery of the tread portion 15 of the tire 11 bulges by vulcanization so that the central portion protrudes radially outward from both ends, and is usually curved with a constant radius of curvature. As a result, in the third and fourth belt plies (parallel belt plies) 26c and 26d constituting the tire 11, the radii Qc and Qd from the rotation center of the tire 11 to the center Hr in the width direction are the rotation centers of the tire 11. To both ends Hc and Hd in the width direction are larger than the radii Nc and Nd, and there are radial differences Kc and Kd, respectively. Here, the amplitude a, wavelength λ, radius Qc, Qd, Nc, and Nd of the cord 28 described above are obtained by measuring each value by X-ray or the like after assembling the vulcanized tire 11 and filling the inner pressure. Here, the rim is a standard rim of the following standard, and the internal pressure is the air pressure with respect to the maximum load (maximum load load) of a single wheel. Further, the above-mentioned standard is determined by an industrial standard that is effective in an area where tires are produced or used. For example, in the United States, “The Tire and Rim Association Inc. Year Book”, in Europe “The European Tire and Rim Techenical Organization Standards Manual”, and in Japan “Japan Auto Tire Association” JATMA Year Book. ing.
[0009]
The tire 11 as described above is formed by molding a green tire and then vulcanizing the green tire with a vulcanizer. This green tire is a cylindrical molding drum (not shown). After the carcass ply 22 is wound around the outer periphery of the carcass layer 21 to form the carcass layer 21, the bead core 12 is set outside the carcass layer 21 and folded to form a cylindrical green case, as shown in FIG. A plurality of (five) belt plies 26, that is, the first, second, third, fourth, and fifth belt plies 26a, 26b, 26c, 26d, and 26e are wound around the outer periphery of the band forming drum 35 one after another. Then, a tread 31 is wound around the outside of the belt layer 25 in the radial direction to form a BT (belt tread) band 36. At this time, the third and fourth belt plies 26c and 26d, which are parallel belt plies, are formed by spirally winding a rubber-coated ribbon-like body with one or several cords 28 bent in a wave shape. As a result, the cords 28 in the third and fourth belt plies 26c and 26d are arranged so as to be substantially parallel to the circumferential direction. Here, the band forming drum 35 described above has a smaller radius from the center of rotation to the outer periphery as it goes from the center in the axial direction to both outer sides in the axial direction. As a result, when winding the inclined belt ply and the parallel belt ply, Both have a drum shape as a whole. As a result, the radius Rr at the axial center Cr of the band forming drum 35 is equal to the widths Wc and Wd of the third and fourth belt plies (parallel belt plies) 26c and 26d from the axial center Cr of the band forming drum 35. It is larger by the radius differences Sc and Sd than the radii Rc and Rd at the positions Pc and Pd that are respectively separated by 1/2 on the both axial outer sides. In this embodiment, the radius differences Sc and Sd are equal to or larger than the radius differences Kc and Kd in the third and fourth belt plies 26c and 26d of the vulcanized pneumatic tire 11 described above, respectively. When the curvature radii of the third and fourth belt plies 26c and 26d in the longitudinal section including the axis are a predetermined value, the curvature radius of the outer periphery of the band forming drum 35 in the longitudinal section including the axis is less than the predetermined value. It becomes. Then, when the BT band 36 is formed using such a band forming drum 35, the BT band 36 is fitted and affixed to the outer side in the radial direction while the green case is expanded in a substantially semicircular cross section. Mold green tires.
[0010]
Thereafter, the above-described green tire is accommodated in a vulcanizer and vulcanized. During this vulcanization, the third and fourth belt plies 26c and 26d (parallel belt plies) constituting the BT band are expanded in diameter as a whole. . Here, as described above, since the radial differences Sc and Sd are equal to or larger than the radial differences Kc and Kd, the diameter expansion amounts of the third and fourth belt plies 26c and 26d are the center portion in the width direction and both end portions in the width direction. Or larger at both ends in the width direction than at the center portion in the width direction. As a result, the circumference of the corrugated cord 28 embedded in the width direction both ends of the third and fourth belt plies 26c and 26d during vulcanization is increased. The amount of stretching in the direction is equal to or greater than the amount of stretching of the wavy cord 28 embedded in the central portion in the width direction. As a result, the value obtained by dividing the average amplitude of the cords 28 at both ends in the width direction of the third and fourth belt plies 26c and 26d in the vulcanized pneumatic tire 11 by the average wavelength, that is, the value A of a / λ is the width A value obtained by dividing the average amplitude of the cord 28 in the central portion in the direction by the average wavelength, that is, a value B of a / λ or less. In this way, by using the band forming drum 35 described above, the tire 11 having the value A equal to or less than the value B can be formed easily and reliably.
[0011]
As described above, the value A of a / λ at the widthwise ends of the third and fourth belt plies 26c and 26d (parallel belt plies) is equal to or less than the value B of a / λ at the widthwise center. If the value B is equal to or less than the value B, the circumferential rigidity at the both ends in the width direction of the third and fourth belt plies 26c, 26d, that is, the squeezing effect is increased by being greatly stretched during vulcanization. It is possible to increase the rigidity in the central portion in the width direction to be equal to or higher than the circumferential rigidity, that is, equal to or exceeding this, and as a result, the belt end separation can be effectively suppressed.
[0012]
【Example】
Next, test results will be described. In this test, the A / B values of the third and fourth belt plies are 1.4 and 1.4, respectively, and the A / B values of the third and fourth belt plies are 0.9 and 0.9, respectively. A test tire was prepared. Here, the structure of the belt layer of each tire was the same as that described in the above embodiment, the size of each tire was 265 / 60R22.5, and the rim on which each tire was mounted was 8.25. Next, after filling each of these tires with an internal pressure of 900 kPa, running on a drum while increasing a longitudinal load of 2725 kgf from a speed of 60 km / h in steps of 5 km / h every 30 minutes. The speed at which belt end separation occurred was obtained. When the result is indicated by an index of 100 for the conventional tire, the durability of the belt was improved to an index of 125 for the test tire. Here, the index 100 was 115 km / h.
[0013]
In addition, after filling the tire with an internal pressure of 900 kPa, belt end separation occurs by running on the drum at a speed of 60 km / h while applying a longitudinal load of 2725 kgf and a lateral load of 275 kgf (10% of the longitudinal load). The distance traveled was determined. When the result is indicated by an index of 100 for the conventional tire, the durability of the belt improved to an index of 130 for the test tire. Here, the index 100 was 1800 km.
[0014]
Next, four tires were prepared, and after these tires were mounted on commercial trucks and filled with an internal pressure of 900 kPa, paving highway 30% and paving general road 70% while applying an average load of 2600kgf. The road was run for 100,000 km, and at the end of the run, each tire was dissected and the crack length along the cord of the inclined belt ply was measured for 20 cords. As a result, the average of the conventional tire was 5.4 mm, but the test tire decreased to an average of 1.8 mm, and the separation resistance was improved.
[0015]
【The invention's effect】
As described above, according to the present invention, the circumferential rigidity at the end of the belt, that is, the effect of tightening can be enhanced, so that the belt durability is improved.
[Brief description of the drawings]
FIG. 1 is a meridian cross-sectional view of a pneumatic tire showing an embodiment of the present invention.
FIG. 2 is a partially broken plan view thereof.
FIG. 3 is a plan sectional view showing a cord in a parallel belt ply.
FIG. 4 is a partial front view of a pneumatic tire molding drum.
[Explanation of symbols]
11 ... Pneumatic tire 21 ... Carcass layer
22 ... Carcass ply 25 ... Belt layer
26 ... belt ply 26c, 26d ... parallel belt ply
28 ... code 31 ... tread
35 ... Drum 36 ... Band
Cr ... Center in the axial direction Rr ... Radius
Pc, Pd ... position Sc, Sd ... radius difference
Hr ... Axial center Hc, Hd ... Axial ends
Kc, Kd ... radius difference

Claims (1)

    An inclined belt ply in which a cord that is inclined with respect to the tire equatorial plane is embedded, and a parallel belt ply in which a cord that is bent in a wavy shape is embedded are wound around the outer periphery, and the radius starts from the center in the axial direction. It has a drum-like shape with a smaller diameter toward the outer sides in the axial direction, and the radial difference between the axial center and a position that is separated from the axial center by 1/2 width of the parallel belt ply to the outer sides in the axial direction. A step of preparing a tire-forming drum having a radial difference greater than or equal to the radial difference between the center in the width direction and both ends in the width direction of the parallel belt ply of the vulcanized pneumatic tire having the parallel belt ply, and the drum-shaped drum By winding a plurality of inclined belt plies and parallel belt plies around the outer periphery, the cord in the parallel belt ply is substantially parallel to the circumferential direction. A belt layer is formed while arranging the belt layers, and then a tread is wound around the outer side of the belt layer to form a band of a pneumatic tire, and the pneumatic case is expanded outward of the green case while expanding the green case. A method for manufacturing a pneumatic tire, comprising: a step of fitting a tire band to form a pasted green tire; and a step of vulcanizing the green tire to manufacture a pneumatic tire.

Images